Have a 24 x8 router table. Has limit and home switches on all 3 axis.  Every thing works fine and it does route good.

The problem I have is when I first set it up,   I do a ref all home and X and Y go to home and back off fine,

 but Z goes to home and does not back off. I have set the Off Home to .1"

Z homes at the top, and it does turn on the green lites around the Z zero button. It has worked properly before but has stoped recently.

What am I missing?

First thing is that Home Off does not make it move a distance, what it is for is if your home switch is a distance away from the machine zero you can set that distance as a Home Off. When you home the machine coords will show that distance rather than showing Zero, that way Mach will know how far you are away from the actual machine zero position when you home.

Sounds like you either have noise on the Z wiring or the switch is not great and is bouncing. The Green shows that Mach has seen the switch open then close after reversing so Mach is working fine but the switch is not. You could try setting an Debounce interval of 2000 on General Config page but I personally prefer to fix the problem rather than have Mach mask it.
Hood